DISCRETE I/O
The values returned in the discrete input words are determined by what has been
written into the discrete output words. By writing the correct words, values stored in
parameters can be accessed.
Discrete I/O does not allow write access to the parameters. That is, parameters cannot
be changed via a Remote I/O. In order to effect this type of operation, communication
must be carried out using Block Transfer. However, output word 7 allows scan point
priority of the Milltronics device to be altered.
The number of discrete input and output words available is determined by the rack size
as configured on the SmartLinx module. Each 1/4 rack allows two words each for
discrete inputs and outputs.
rack size
number of discrete input or
words
discrete output words
1/4 rack
2
0, 1
1/2 rack
4
0, 1, 2, 3
3/4 rack
6
0, 1, 2, 3, 4, 5
full rack
8
0, 1, 2, 3, 4, 5, 6, 7
In full rack configuration, discrete output word 7 may be used to configure the returned
data in discrete input word 7. This data is written in output word 7, bits 0–9 where each
bit corresponds to a transducer 1–10. The meaning of those bits is determined by
writing to bits 10–15 of output word 7, as described in the following section.
It is convenient to note the similarity between the input and output areas.
Discrete Output Words
output word
description
0
communication control
1
point and parameter number, word 1
2
point and parameter number, word 2
3
point and parameter number, word 3
4
point and parameter number, word 4
5
point and parameter number, word 5
6
point and parameter number, word 6
7
point status control
PL-533
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Milltronics SmartLink 3/31/97 1:16 PM Page 18
